Elbow Ulnar Collateral Ligament Injury: A Guide to Diagnosis and Treatment

Now in a fully revised and expanded second edition, this practical text presents the current state of the art and latest advancements in the biomechanics, assessment, diagnosis and management of UCL injury in the elbow. In the years since this book’s initial publication, significant developments have occurred on multiple fronts relating to elbow UCL injury, including injury prevention, less invasive repair techniques, more anatomical surgical reconstructions, and improved post-injury rehabilitation protocols. Chapters are once again arranged thematically, beginning with discussion of the relevant anatomy and surgical approaches, throwing biomechanics and overload mechanisms, epidemiology, history and physical exam. After a description of the radiological approaches to assessment, both conservative and surgical strategies are outlined and discussed in detail, from repair both with and without augmentation to reconstruction both arthroscopically and with newer minimally invasive techniques. Considerations for UCL injury in special populations – the young athlete and the female athlete – and sports-specific rehabilitation, return-to-play and prevention via wearable technology round out this thorough presentation. 
Enhanced with select video clips illustrating surgical techniques, Elbow Ulnar Collateral Ligament Injury, Second Edition remains a go-to resource for orthopedic surgeons, sports medicine specialists, therapists and trainers who work with athletes that suffer from these conditions.

• Language: English
• Publisher: Springer
• Release date: May 13, 2021
• ISBN: 9783030695675

Book preview

© Springer Nature Switzerland AG 2021

J. S. Dines et al. (eds.)Elbow Ulnar Collateral Ligament Injuryhttps://doi.org/10.1007/978-3-030-69567-5_1

1. Anatomy and Biomechanics of the Medial Ulnar Collateral Ligament

Miguel Pelton¹, Salvatore J. Frangiamore¹   and Mark S. Schickendantz¹

(1)

Cleveland Clinic Sports Medicine, Cleveland Clinic Foundation, Garfield Heights, OH, USA

Keywords

Medial ulnar collateral ligamentBiomechanics of medial side of the elbowValgus overloadDynamic restraintsStatic restraints

Introduction

The medial ulnar collateral ligament (MUCL) has three distinct components. These include the anterior bundle, posterior bundle, and transverse or oblique ligament. The anterior bundle of the UCL complex is the primary static stabilizer to valgus stress on the medial elbow. It primarily acts to resist valgus and extension stress from 70 to 120° of elbow flexion. The anterior bundle of the UCL is composed of an anterior and a posterior band. The anterior band is more isometric, but generally tight in extension, whereas the posterior band is tight in flexion. The posterior bundle is a fan-like structure that originates from the medial epicondyle and inserts into the medial posterior aspect of the olecranon. Lastly, the transverse bundle is often indistinguishable from the capsule and has both its origin and insertion on the proximal ulna at the olecranon and sublime tubercle, respectively.

The mean length and width of the anterior bundle of the UCL is 31.9 mm (range 21.1–53.9 mm) and 5.95 mm (range 4.5 mm–7.6 mm), respectively [1–8]. The anterior bundle originates at the medial epicondyle of the humerus at approximately 8.5 mm distal and 7.8 mm anterior to the center of medial epicondyle of the humerus with a surface area of 17–45 mm [1]. The anterior position relative to the medial epicondyle is important to conceptualize during UCL reconstruction, as posterior tunnel position is a common error. This can decrease graft isometry and result in a graft which is overly tight in flexion [9] (Figs. 1.1 and 1.2).

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Fig. 1.1

Correct and incorrect tunnel reconstruction in both sagittal and coronal planes

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Fig. 1.2

Illustration demonstrating Docking technique with correct tunnel trajectories and allograft reconstruction in place

The exact distal insertion site of the anterior bundle has been a topic of controversy [1, 4, 10]. It was once described at the apex of the sublime tubercle, at a site 5.5 mm distal to the articular surface. Now, more recent literature suggests a more elongated, tapered footprint measuring 66.4–187.6 mm², and an average of 5.3 mm (1.5 mm–7.6 mm) distal to the center of the sublime tubercle along the ulnar UCL ridge [1–3, 5–7, 10–13] (Fig. 1.3). Those authors suggest that the wide variability of distal attachments may be due to the inclusion of the underlying joint capsule in addition to the tendinous structure of the AB of the anterior bundle. It remains to be seen if changes to distal tunnels should be made to better reconstruct native anatomy [14–17]. Camp and colleagues recently assessed an alteration to the distal tunnel insertion using cadaveric reconstructions with palmaris autograft versus the traditional docking technique [18]. They demonstrated a higher mean ultimate load to failure with anatomical reconstruction over the traditional docking technique [18].

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Fig. 1.3

Medial side of the elbow demonstrating the expanded ulnar footprint of the anterior bundle of the ulnar collateral ligament . (a) insertion length, (b) articular surface to proximal ulnar footprint 5.5 mm, (c) center of humeral footprint to the center of ulnar footprint, (d) length of distal humeral origin surface area 17–45 mm² (center of origin 8.5 mm distal and 7.8 mm lateral to medial epicondyle)

Biomechanics of Medial Ulnar Collateral Ligament Complex

Anterior Bundle (Anterior Band, Posterior Band, and Central Band)

The primary biomechanical role of the mUCL is to provide valgus stability of the elbow, especially in overhead throwing athletes. Morrey et al. demonstrated that with an intact radial head, the mUCL provides 31% and 54% of valgus stability of 0° and 90° of elbow flexion, respectively [6, 19]. Moreover, the authors noted that an intact mUCL allowed for only 3° of valgus opening in full extension and 2° of valgus opening in full flexion.

Similar findings have been reported in several other studies, which have demonstrated 2° to 8° of valgus laxity with an intact mUCL [2, 20, 21]. To quantify when the mUCL has the most laxity with a loaded elbow, Safran et al. analyzed 12 cadaveric specimens with 2 Nm load applied to the elbow in 30° of flexion and reported 10.7° of valgus laxity with the forearm in neutral rotation [8]. Callaway et al. expanded on these findings by loading the elbow with 2 Nm at 30° and 90° of flexion and reported a valgus laxity of 3.6° [22]. The former of these two studies did not quantify the amount of inherent valgus laxity specimens had prior to testing, which makes direct comparison of the two studies challenging. However, it is thought the amount of mUCL valgus laxity is greatest at 30° of flexion [8].

The anterior bundle has been shown to impart the greatest resistance to valgus loads. It is not an isometric stabilizer but changes length throughout progressive elbow flexion [23–25]. Studies have demonstrated a change of 2.8–4.8 mm as the elbow progresses from extension to full flexion [20, 26]. One cadaveric sectioning study sought to define the contribution to valgus stability of three distinct sections of the anterior bundle insertion [27]. They describe the proximal, middle, and distal third segments of insertional footprint at the sublime tubercle. A 5 Nm valgus load was applied at 30°, 60°, 90°, and 120° of flexion. Ulnohumeral joint gapping showed no significant difference between the intact state and sectioning of both the middle and distal insertion segments. However, there was a significant difference in joint gapping when the proximal segment was sectioned. One reason for this may be the relative thinning of the AB as it inserts distally on the sublime tubercle. In 16 cadaveric specimens, Frangiamore et al. found the posterior distal portion of the AB contributed the most to overall valgus elbow rotational stability and stiffness [28]. This was most apparent at 90° and 120° of elbow flexion. Those authors also found that the anterior insertions contributed most to elbow stability at lower flexion angles [28]. Thus, reconstruction techniques may take all these properties into account as more investigations are performed.

Some literature suggest that the presence of the middle or central band acts as an adjunct to impart some valgus stability [23, 28, 29]. Unlike the anterior and posterior bands, this central band was originally thought to be relatively static and taut throughout elbow motion [28]. One recent biomechanical cadaveric study sought to understand the load distribution between the anterior and posterior bands of the AB during the range of motion through the transition point of the central band [30]. The three bands were sequentially transected and then load tested in varying angles with valgus stress. The lesser flexion angles, 0° and 30°, saw the highest slack in the posterior band and the highest structural stiffness in the anterior band. The authors concluded that at higher flexion angles of 60–90°, the anterior band saw the highest slack and the middle band demonstrated the greatest stiffness. Further in vitro research is needed to further elucidate the role of the proposed central or middle band of the anterior bundle MUCL with pertinent clinical applications.

Posterior Bundle

Several studies have sought to define the contribution of the posterior bundle of the mUCL to valgus stability by sectioning the mUCL and measuring valgus angles during elbow range of motion [22, 31–34]. The posterior bundle (PB) of the UCL is a broader and thinner part of the UCL complex, originating from the humeral epicondyle and broadly inserting on the medial ulna. The PB provides valgus stability at flexion angles >120° [21]. Rahman et al. built a computational elbow joint model simulating varying levels of MUCL deficiencies [35]. When either the anterior or posterior bundle was transected, there was more valgus instability. However, there was less instability in the posterior bundle deficient condition. Additionally, less contact pressure at the cartilage surface was noted only in the anterior bundle deficient and entire mUCL deficient conditions. In agreement with other literature, these data indicate a smaller role of the posterior bundle in imparting medial elbow joint stability [36–40].

Transverse Ligament

The transverse ligament of the MUCL was thought not to impart any inherent stability as it does not cross the ulnohumeral joint, is not consistently present, or is poorly developed [19, 22, 23]. Others suggest that it is the confluence of collagen fibers from the transverse bundle with the anterior bundle that can contribute to valgus stability [10, 38]. Kimata and colleagues recently describe this connection in 42 cadaveric specimens [39]. The transverse bundle contributed to the distal half of the anterior bundle insertion in 73% of the elbows (Type I). In the remaining 27% of specimens, the transverse bundle contributed to the entire anterior bundle insertion (Type II). Female cadavers were more likely to show Type II anatomy at the medial elbow. These fibers were all represented in a perpendicular fashion to the anterior bundle fibers. Future biomechanical studies will further elucidate what role, if any, the transverse ligament contributes to elbow stability.

Anatomy of the Medial Elbow Complex Dynamic Stabilizers

The dynamic stabilizers of the elbow are made up of the flexor–pronator muscle complex that cross the elbow joint. Specifically, the flexor digitorum superficialis (FDS), flexor carpi ulnaris (FCU), pronator teres (PT), and brachialis (BR) make up what is often referred to as the flexor–pronator mass . They play an integral role in valgus stability during the throwing motion and studies have demonstrated an increased risk of UCL injury when these are deficient [32]. The medial antebrachial cutaneous nerve arises from the medial cord of the brachial plexus. This nerve must be observed and retracted in any proposed reconstruction incision (Fig. 1.4). The forearm flexors primarily insert proximally on the humerus as part of the common flexor insertion, 4.4 mm posterior to the medial epicondyle [1]. The common flexor insertion has been reported to have a surface area of 127.9 mm² (range, 89.5–166.3 mm²) [1, 10]. The FDS and FCU also have demonstrated secondary ulnar insertions near the attachment of the AB of the UCL [33]. The FDS ulnar tendinous insertion has been reported to be overlapped with the AB for 46% of its length, until inserting 6.8 mm distal to the sublime tubercle of the ulna [1]. The FCU ulnar insertion has been reported to be 1.9 mm posterior and 1.3 mm proximal to the sublime tubercle and overlaps 21% with the AB during its proximal to the distal course (Fig. 1.5).

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Fig. 1.4

Illustration demonstrating the contents and relationships of the flexor–pronator mass . (a) Dashed line indicates incision for MUCL reconstruction

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Fig. 1.5

(a) Illustration and (b) cadaveric view of relationship of ulnar insertion of the anterior bundle of the UCL and the ulnar footprints of the FCU and FDS

The pronator teres (PT) inserts just proximal to the common flexor humeral insertion, 9.4 mm proximal from the medial epicondyle. The footprint of this humeral insertion has been reported to be 40.1 mm² (range, 33–47 mm²) [1]. The PT then courses distally to insert 14.5 mm distal to the sublime tubercle, which is 24.5 mm distal to the joint line. It should be highlighted that the PT ulnar insertion is a thin tendinous structure that runs between the brachialis muscle and the anterior bundle of the UCL.

Microanatomy and Biomechanical Properties

The microstructural organization of the mUCL as it relates to biomechanical properties has recently been investigated [36, 37, 40]. Smith and colleagues performed a cadaveric study using tensile forces to measure real-time microstructural collagen changes in 34 specimens [36]. Through the use of a polarization camera, the characteristics stress–strain curve could be obtained for both the anterior and posterior bundles. The AB was found over the PB to have a larger elastic modulus in both the toe region (2.73 MPa [interquartile range, 1.1–5.6 MPa] vs 0.65 MPa [0.44–1.5 MPa respectively) and the linear region (13.77 MPa [4.8–40.7 MPa] vs 1.96 MPa [0.58–9.3 MPa] respectively). Additionally, the AB demonstrated larger stress values, stronger collagen alignment, and more uniform collagen organization during stress-relaxation. The posterior bundle collagen fibers showed more disorganized fibers in zero, transitional and linear regions of the stress–strain curve. However, under loading, the magnitude of change of the collagen fibers was minimal. These authors opine that the data provide a basis to describe the relatively static nature of the mUCL bundles which is not well suited to large tensile forces. In comparison to the other ligaments, such as the ACL and PCL, microstructural properties of the UCL change less under load. The overall alignment is weaker and more dispersed before the application of load. These data may explain why mUCL is less compliant and more vulnerable to injury with the high valgus loads that may be seen during throwing.

Conclusion

The anterior bundle of the medial ulnar collateral ligament is responsible for the primary valgus stability of the elbow. Proximally, it inserts in an anterior and distal position relative to the center of the epicondyle and distally at the sublime tubercle with an elongated tapered insertion. Distally, the UCL is intimately associated with ulnar attachment of the forearm flexors and must be taken into consideration during dissection. With an increased understanding of the anatomy and biomechanics of the UCL and its anatomic relationships, reconstruction approaches and techniques can be further refined to reflect these changes.

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© Springer Nature Switzerland AG 2021

J. S. Dines et al. (eds.)Elbow Ulnar Collateral Ligament Injuryhttps://doi.org/10.1007/978-3-030-69567-5_2

2. Clinically Relevant Elbow Anatomy and Surgical Approaches

Xinning Li¹   and L. T. C. Josef K. Eichinger²

(1)

Sports Medicine and Shoulder Surgery, Department of Orthopaedics, Boston University School of Medicine, Boston, MA, USA

(2)

Shoulder and Elbow Surgery, Department of Orthopaedics, Medical University of South Carolina, Charleston, SC, USA

Keywords

Ulnar collateral ligamentElbow anatomySurgical approachesSublime tubercleMuscle-splitting approachFlexor–pronator mass elevationElbow arthroscopy

Pertinent Anatomy of the Thrower’s Elbow

Osseous Anatomy

The elbow is primarily a ginglymus or hinge joint, but in reality consists of three bony articulations including ulnohumeral, radiocapitellar, and radioulnar joint. The primary arc of motion during throwing motions is flexion and extension through the ulnohumeral articulation; however, some pronation–supination does occur through the ulnohumeral and radioulnar joints. In full extension, the elbow has a normal valgus-carrying angle of 11–16°. Morrey and An determined the osseous anatomy’s contribution to resistance to valgus stress remains fairly constant throughout elbow motion [1]. In full extension, roughly one-third of valgus force was resisted by the ulnar collateral ligament (UCL) (31%), one-third by the anterior capsule (38%), and one-third by the bony architecture (31%). At 90° of flexion, the UCL increased its relative contribution to 54%, whereas the anterior capsule provided only 10% to valgus stability, and the bony anatomy contribution remained relatively unchanged at 36%.

Muscular Anatomy

Flexor–Pronator Mass

The flexor–pronator mass is a collection of muscles that form a common origin from the medial epicondyle. These muscles can be viewed and organized into superficial and deep layers or groups. Pronator teres, flexor carpi radilais (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), and palmaris longus (PL) muscle are found in the superficial layer. In the deep layer, three muscles are found and composed of flexor digitorum profundus (FDP), flexor pollicus longus (FPL), and pronator quadratus (PQ) muscles (Fig. 2.1). The combined function is to perform wrist flexion and forearm pronation. An analysis of the primary muscles of the flexor–pronator group (pronator teres, FDS, FCU, and flexor carpi radialis) indicates that their dynamic action applies a varus moment and therefore resisting valgus force across the elbow [2]. In relation to throwing mechanics; however, electromyogram (EMG) studies indicate that the flexor muscles do not reflect a compensatory increase in activity in throwers with valgus instability. Furthermore, both flexor carpi radialis and pronator teres show a paradoxical decrease in activity in throwers with valgus instability after medial ulnar collateral ligament (MUCL) rupture [2, 3]. It is unclear whether the decrease in EMG activity is a cause or effect of MUCL injuries. Despite these EMG findings, ruptures of the flexor–pronator mass and medial epicondylitis can occur in the clinical setting of MUCL injuries of throwers indicating some level of contribution of the muscles to function and likely stability [4, 5]. An anatomic analysis revealed that the FCU muscle is the predominant musculotendinous unit overlying the UCL essentially independent of elbow flexion and forearm rotation [6]. The only other muscle with less frequent contribution to coverage was the FDS. Several authors have reported FCU as the biggest contributor to valgus stability in MUCL deficient elbows [7, 8]. In contrast, despite suboptimal muscle coverage, Udall et al. [9] showed FDS as the greatest contributor to valgus stability of the elbow due to its bulk (increased cross-sectional area). Furthermore, Hoshika et al. reported that contraction of the FDS of the index and middle fingers contributes the most to stabilization of the elbow against valgus stress [10].

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Fig. 2.1

Anterior view of the superficial and deep components of the elbow flexor–pronator mass

Palmaris Longus Tendon

The PL tendon is an ideal source of graft for MUCL reconstruction; however, it is clinically absent in 15% of the population with incidences varying widely depending on ethnicity [2]. Clinically, the presence of the PL can be verified by opposing the thumb and small finger together, which creates a characteristic appearance over the volar surface of the wrist (Fig. 2.2). The PL tendon is located between the flexor carpi radialis tendon and the FDS tendons at the level of the wrist.

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Fig. 2.2

The presence of the palmaris longus can be verified preoperatively by opposing the thumb and small finger together, which creates a characteristic appearance over the volar surface of the wrist

Nerve Anatomy

Medial Antebrachial Cutaneous Nerve

The medial antebrachial cutaneous nerve arises from the medial cord of the brachial plexus. In the distal brachium, the nerve travels medial to the brachial artery. The nerve then courses down the ulnar aspect of the forearm and enters the deep fascia with the basilica vein. It is responsible for sensation over the medial aspect of the elbow. Branches pass 3–60 mm distal to the medial epicondyle and are at risk with the typical longitudinal incision used in UCL reconstructive surgery [11]. Identification and protection of these nerve branches protect from iatrogenic injury and prevent the development of painful, symptomatic neuromas or superficial sensory derangement. The nerves are encountered immediately after skin incision (Fig. 2.3) and are variable in their size, appearance, and distribution [12].

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Fig. 2.3

The medial antebrachial sensory nerve is encountered immediately after the skin incision during the approach for the UCL reconstruction. Care is taken to identify and protect this nerve throughout the procedure to prevent injury

Ulnar Nerve

The surgical approach to the UCL demands a clear understanding of the location of the neurovascular structures. The ulnar nerve is the most thought of neurologic structure in regard to UCL reconstructive surgery. The ulnar nerve descends along the posteromedial aspect of the humerus and then enters the cubital tunnel posterior to the medial epicondyle (Fig. 2.4). After exiting the cubital tunnel, the ulnar nerve gives off an articular sensory innervation branch and then enters the flexor compartment of the forearm. It is positioned under the FCU adjacent to the ulna. The nerve innervates the FCU and the medial half of flexor digitorum profundus.

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Fig. 2.4

The ulnar nerve descends along the posteromedial aspect of the humerus and then enters the cubital tunnel posterior to the medial epicondyle

The ulnar nerve courses with the ulnar artery and distally in the hand it is responsible for sensory innervation of the ulnar 1.5 digits and intrinsic hand motor function as well. A muscle-splitting approach for UCL reconstruction can be performed without detachment of the flexor–pronator mass of the forearm [11, 13]. Exposure for this technique is performed either through a naturally occurring raphe that delineates the separation between the FCU and the remaining flexor muscle mass or simply in-line between the medial epicondyle and sublime tubercle (Fig. 2.5). This region is a natural watershed area between motor innervation of the ulnar nerve and median nerve as verified through cadaveric analysis. This approach, therefore, avoids iatrogenic denervation to these muscles [11, 13]. It is essential that during the muscle splitting approach that a sharp retractor is never used posterior medially to prevent injury to the ulnar nerve (Fig. 2.6).

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Fig. 2.5

Exposure for the muscle-splitting approach is performed through a naturally occurring raphe that delineates the separation between the flexor carpi ulnaris and the remaining flexor muscle mass (blue dots) or simply in-line between the medial epicondyle and sublime tubercle

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Fig. 2.6

Muscle-splitting approach is performed with the ulnar nerve in the cubital tunnel (blue dots). Sharp retractors should never be used in the posterior and medial direction to prevent iaotrogenic injury to the ulnar nerve

Ligamentous Anatomy

Medial Ulnar Collateral Ligament

The medial ulnar collateral ligament (MUCL) of the elbow is composed of three bundles, including the anterior, posterior, and transverse bundles [1, 14]. The transverse bundle has also been described as the oblique bundle [13]. The anterior bundle is composed of two different histological layers and two different functional bands. The deep layer is confluent with the joint capsule, while the superficial layer is a more distinct structure above the capsule with thick parallel fibers with a mean width of 4–5 mm [15]. An anatomic and biomechanical evaluation of the MUCL revealed that the anterior bundle can be further delineated into two distinct functional sub-units, the anterior and posterior bands [16]. The anterior and posterior bands of the anterior bundle of the MUCL perform reciprocal functions with the anterior band functioning as the primary restraint to valgus rotation at 30°, 60°, and 90° of flexion. The anterior and posterior bands are equal functioning restraints at 120° of flexion while the posterior band acts as a secondary restraint at 30° and 90° of flexion (Fig. 2.7) [16].

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Fig. 2.7

Illustrations of the anatomy of the medial collateral ligament (MCL) of the elbow at 30°, 60°, 90°, and 120° of flexion. The anterior bundle arises from the inferior aspect of the medial epicondyle (ME) and inserts immediately adjacent to the joint surface on the ulna near the sublimis tubercle. The anterior bundle widens slightly from proximal to distal and can be subdivided into anterior and posterior bands of equal width. The bands tighten in a reciprocal fashion as the elbow is flexed and extended (bottom frame), and they are separated by easily identifiable isometric fibers (arrows). The posterior bundle arises from the ME slightly posterior to its most inferior portion. It inserts broadly on the olecranon process. The posterior bundle appears to be thickened joint capsule when the elbow is extended. As the elbow is flexed, the ligament tightens and fans out to form a sharp edge that is perpendicular to the long axis of the ulna

The anterior bundle arises from the inferior aspect of the medial epicondyle [17] and inserts immediately adjacent to the joint surface on the ulna near the sublimis tubercle. The anterior bundle widens slightly from proximal to distal and can be subdivided into anterior and posterior bands of equal width. The bands tighten in a reciprocal fashion as the elbow is flexed and extended (bottom frame), and they are separated by easily identifiable isometric fibers (arrows). The posterior bundle arises from the medial epicondyle slightly posterior to its most inferior portion. It inserts broadly on the olecranon process. The posterior bundle appears to be a thickened joint capsule when the elbow is extended. As the elbow is flexed, the ligament tightens and fans out to form a sharp edge that is perpendicular to the long axis of the ulna. Furthermore, the anterior bundle originates from the anteroinferior edge of the medial humeral epicondyle with an origin measuring 45.5 ± 9.3 mm² in diameter and inserts onto the sublime tubercle on the ulna in an area measuring 127 ± 35.7 mm² in diameter [18].

The anterior bundle of the MUCL is the primary restraint to valgus stress from 20° to 120° of flexion and is the critical structure requiring reconstruction after injury in throwers. Because its origin is slightly posterior to the axis of the elbow, there is a cam effect created so that the ligament tension increases with increasing flexion. The anterior bundle of the MUCL is the strongest of the different components with a mean load to failure of 260 N [19]. The posterior bundle is not a significant contributor to valgus stability unless the remaining structures of the MUCL are sectioned. The posterior bundle of the MUCL is thinner and weaker than the anterior bundle, originates from the medial epicondyle and inserts onto the medial margin of the semilunar notch and acts only as a secondary stabilizer of the elbow beyond 90° of flexion [20]. Lastly, the oblique bundle or transverse ligament does not span the ulnohumeral joint but instead acts to increase the greater sigmoid notch as a thickening of the joint capsule [21].

Relevant Surgical Approaches

Positioning

UCL reconstruction is performed with the patient under either regional block or general anesthesia in the supine position with the extremity outstretched onto an arm board. A pneumatic tourniquet is placed on the upper arm and inflated to 200–250 mmHG during the graft harvest and critical portions of the procedure. Routine sterile prep and drape of the extremity is done under sterile conditions. Diagnostic elbow arthroscopy is performed before graft harvest and UCL reconstruction.

Elbow Arthroscopy

Arthroscopic evaluation is performed with the operative extremity in an arm holder and positioned across the patient’s chest utilizing the Spider Limb Positioner (Smith & Nephew, Tenet Medical Engineering, Memphis, TN) (Fig. 2.8). An 18-gauge spinal needle is used to enter the joint via the soft spot or direct lateral portal that is located in the middle of a triangle formed by the lateral epicondyle, radial head, and olecranon. Forty to 50 ml of normal saline is injected to distend the elbow joint before trocar insertion to prevent articular cartilage damage. Distension of the joint will move the soft tissue along with the neurovascular structures away from the capsule, thus minimizing the risk of injury. The direct or mid-lateral (ML) portal (Fig. 2.9) is excellent for viewing and evaluations of the posterior compartment, specifically, the radioulnar joint, inferior surfaces of the capitellum, and radial head. It is relatively safe, passes between the plane between the anconeus and triceps muscle and within 7 mm of the lateral antebrachial cutaneous nerve [22, 23].

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Fig. 2.8

Arthroscopic elbow evaluation is performed with the operative extremity in an arm holder and positioned across the patient’s chest utilizing the Spider Limb Positioner. (Smith & Nephew, Tenet Medical Engineering, Memphis, TN)

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Fig. 2.9

Commonly utilized elbow arthroscopy portals for evaluation prior to the UCL reconstruction procedure. Midlateral (M.L.), Anterolateral (A.L.), Posterolateral (P.L.), and Trans-triceps (T.T.) portal sites

An anterolateral (AL) portal (Fig. 2.9) is the first portal established in the elbow arthroscopy sequence before the UCL reconstruction to examine the anterior and medial elbow compartment. More importantly, we perform an arthroscopic stress test on every patient to confirm valgus instability. This is done (viewing from the AL portal) with the forearm in full pronation and the elbow in 70° of flexion, an opening of 2 mm between the humerus and ulna with valgus stress is considered a positive sign of valgus instability. The AL portal is preferred for examination and viewing of the anterior and medial side of the elbow joint. Andrews and Carson [24] originally described this portal position as 3 cm distal and 1 cm anterior to the lateral epicondyle. Recent anatomic cadaver studies have shown that the 3 cm distal location places the trochar in very close proximity to the radio nerve, which significantly increases the risk of injury [17, 25]. Thus, several authors have moved this portal more anterior and less distal. Plancher et al. [23] advocate an AL portal placed in the sulcus, which is located between the radio head and the capitellum (1 cm distal and 1 cm anterior to the lateral epicondyle). Even with the newer proposed locations, the average distance of the radial nerve to the trochar in the AL portal position is between 3 and 7 mm in nondistended joints [17, 23–25], which increases to 11 mm with joint distension [17].

In order to examine the posteromedial olecranon and humeral fossa for impingement, loose bodies, and spurs, we will establish a second portal posterior and lateral to the triceps tendon (posterolateral portal). The posterolateral (PL) portal location has the largest area of safety provides excellent visualization of the posterior and posterolateral compartments. It is established approximately 3 cm proximal to the tip of the olecranon and at the lateral border of the triceps tendon. Allowing the elbow to flex (20–30°) will relax the posterior capsule and facilitate successful trochar insertion [23]. Structures at risk include the posterior antebrachial cutaneous and the lateral brachial cutaneous nerves. The scope is then advanced distally to the radiocapitellar joint to further evaluate for pathology. If debridement or removal of spurs or loose body is needed in the posteromedial gutter, then another accessory trans-triceps (TT) tendon portal (Fig. 2.9) can be created above the olecranon tip as a working portal for instrumentation. This portal is established above the tip of the olecranon through the musculotendinous junction of the triceps muscle with the elbow in a partially extended position. It is excellent for spur debridement and removing loose bodies from the posteromedial compartment. Structures at risk include the posterior antebrachial cutaneous nerve (23 mm away) and the ulnar nerve (25 mm away) when the elbow is distended [17, 23]. Once the elbow arthroscopy is finished and the graft (palmaris vs. gracillis autograft or allograft) is prepared, the medial approach to the elbow is performed to start the UCL reconstruction.

Medial Approach—Muscle Splitting

All portal sites from the elbow arthroscopy were closed with monocryl before the start of the medial exposure. The arm was then exsanguinated to the level of the tourniquet with an Esmarch bandage. An 9–10 cm incision was made with a #15 blade starting 2 cm proximal to the medial epicondyle and extending along the intermuscular septum to approximately 2 cm beyond the sublime tubercle (Figs. 2.3 and 2.5). Meticulous dissection is performed and the medial antebrachial cutaneous nerve is commonly encountered at this time (Fig. 2.3). We typically tag this nerve with a vessel loop and care is taken to avoid injury or damage. At this time, the common flexor–pronator mass is seen inserting on the medial epicondyle along with the anterior fibers of the FCU muscle. A muscle-splitting approach is performed between the raphe of the FCU and the anterior portion of the flexor–pronator mass (Fig. 2.5) which comprises of the flexor carpi radialis, PL, and the flexor digitorum superficialis. This approach is performed through a true internervous plane between the median nerve (anterior portion of the flexor–pronator mass) and the ulnar nerve (FCU muscle). It is also done within the anatomic safe zone that is defined as the region between the medial humeral epicondyle to the area that is 1 cm distal to the attachment of the anterior bundle of the MUCL on the sublime tubercle [11]. A blunt self-retainer retractor may be used to help with the exposure of the anterior bundle of the MUCL during this step of the operation. A sharp retractor should not be used with the exposure to prevent damage to the ulnar nerve (Fig. 2.6). The UCL is inspected and a longitudinal incision in line with the anterior bundle of the MUCL is made with a deep knife to expose the joint. Subsequently, the sublime tubercle is exposed with a periosteal elevator. Two small homans are placed superiorly and inferiorly to the sublime tubercle to help with the exposure. A small burr (3.0 mm) is used to create two tunnels anterior and posterior to the sublime tubercle perpendicular to each other. A small curette is used to complete the tunnels; care is taken to make sure that a 2 cm bone bridge is left between the two tunnels. At this time, the medial humeral epicondyle is exposed with periosteal elevator and a longitudinal tunnel (along the axis of the epicondyle) is created on the anterior half of the medial epicondyle/UCL footprint with a 4 mm burr (Fig. 2.10). Care is taken not to violate the posterior cortex of the proximal epicondyle, which would place the ulna nerve at risk and compromise graft fixation. See the pertinent chapter for more details on the tunnel position, graft shuttling, and tensioning techniques.

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Fig. 2.10

Surgical approach to the ulnar collateral ligament (UCL) reconstruction . The osseous anatomy includes the humerus, forearm, and the Olecranon (blue star). The ulnar nerve (yellow arrows) is seen behind the medial epicondyle and a single bone tunnel is frilled with a burr into the medial epicondyle (red star). Two converging tunnels are drilled (green arrows) with the burr into the sublime tubercle (orange star) and the palmaris longus graft is passed through the sublime tubercle and docked into the bone tunnel in the medial epicondyle (red star)

Medial Approach—Flexor–Pronator Mass Elevation

Alternative to the muscle-splitting technique is the flexor–pronator mass elevation or takedown described by Jobe et al. [26] as the original medial elbow approach to the UCL reconstruction procedure. A similar medial incision is made centered over the medial epicondyle and extending down past the sublime tubercle. Care is taken to protect both the medial antebrachial cutaneous nerve and the ulna nerve. First, a longitudinal split was made in the fascia and in line with the flexor muscles. At this time, the damaged MUCL is exposed and examined. Additional exposure to the UCL reconstruction procedure is provided with elevation and transection of the common flexor mass along with most of the pronator teres 1 cm distal to the medial epicondyle origin leaving a small stump of tissue for reattachment (Fig. 2.11). This approach has been shown to provide a safe and reliable method for the exposure of the anterior bundle of the MUCL and surrounding anatomy. However, detachment and reattachment of the flexor–pronator mass may create unnecessary morbidity to the patient; thus, several authors have advocated the muscle-splitting technique as a less traumatic approach to the UCL reconstruction procedure without increased risks [11, 27, 28].

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Fig. 2.11

Flexor–pronator mass is transected approximately 1 cm distal to the medial epicondyle origin and retracted to expose the damaged ulnar collateral ligament for reconstruction

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© Springer Nature Switzerland AG 2021

J. S. Dines et al. (eds.)Elbow Ulnar Collateral Ligament Injuryhttps://doi.org/10.1007/978-3-030-69567-5_3

3. Ulnar Collateral Ligament: Throwing Biomechanics

Evan E. Vellios¹  , Kenneth Durham WeeksIII² and David M. Dines³  

(1)

Southern California Orthopedic Institute, Van Nuys, CA, USA

(2)

OrthoCarolina, Charlotte, NC, USA

(3)

Orthopaedic Surgery, Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, USA

David M. Dines

Email: [e-mail]

Keywords

Biomechanics of throwingMedial ulnar collateral ligamentValgus extension overload syndromeBaseballOverhead throwing

Introduction

The overhead throwing motion is created by a complex series of coordinated movements involving different motor groups and the articulations of the upper extremity as well as the kinetic chain. The necessary kinematics of throwing place significant stresses across the joints of the upper extremity, which can lead to potential overload and injury. The shoulder and elbow are most susceptible to injury during throwing. Even though this text is centered upon ulnar collateral ligament (UCL) injury to the elbow, one must be aware of the biomechanics of the entire upper extremity in throwers in order to understand the cause and prevention of such injuries.

Recent technologic advances in motion analysis have given researchers a better understanding of the anatomic, biomechanical, and physiologic demands placed on the shoulder and elbow during throwing. Clearly, changes in kinetics and kinematics during throwing can have a significant effect upon the anatomy and lead to serious, even career-ending injury. For these reasons, it is imperative to have a comprehensive and sport-specific knowledge of muscle recruitment sequences in order to understand potential causes of anatomic failure and subsequent injury. In addition, this fundamental knowledge can lead to the development of better rehabilitation programs to prevent these injuries.

Of all overhead athletes, baseball pitchers are at the greatest risk of acute and chronic upper extremity pathology, particularly injury to the UCL and medial elbow. While some other athletes may be at risk, such as javelin throwers, tennis servers, and even football quarterbacks, pitchers carry the highest risk and have the highest incidence. Epidemiologic studies of injury patterns in baseball players have shown that there are a higher percentage of upper extremity injuries in Division I college players (58%) [1]. In fact, a study by Rothermich et al. showed that 134 (2.5%) out of 5295 Division 1 college baseball players underwent UCL surgery in 2017 alone with most being pitchers and underclassmen [2]. Moreover, a 2019 study by Leland et al. which consisted of a survey of 6135 professional baseball players (Major League, Minor League, and Dominican Summer League) showed a significant increase in the prevalence of UCL reconstruction in young (<30 years old) Minor League players (15–19%) compared to an earlier 2012 study [3]. With regard to Major League Baseball (MLB) specifically, an early study by Conte et al. showed that approximately 30% of player days on the disabled list were the result of shoulder (and elbow) injury with pitchers comprising the majority of disability days at 48%, compared to 20% for outfielders [4]. Most of the injuries pitchers sustained were the result of repetitive overuse of the shoulder or elbow [4]. Furthermore, a recent study by Confino et al. looking at first and second round MLB draft picks from 2008 to 2016 showed that players who underwent early single-sport specialization (played only baseball from high school onwards) had a significantly higher prevalence of upper extremity injuries (primarily shoulder and elbow) and fewer total games played in the MLB than multi-sport athletes [5]. This study highlights the detrimental effects of repeated exposure of the medial elbow to the excessive forces placed upon it during throwing especially in athletes who specialize in a single sport at a young age. The purpose of this chapter is to define the biomechanics in the overhead athlete with a special emphasis upon the biomechanics of the elbow.

Biomechanics of Throwing

As a framework for the understanding of the biomechanics of the throwing shoulder, the pitching cycle is now broken down into six distinct phases, each with its own changes in muscle and joint activity at the shoulder and elbow. During this activity, the thrower must create potential energy generated from the lower extremities and transmitted upward through the pelvis to the trunk and ultimately to the smaller segments of the upper extremity, thereby creating the kinetic energy delivered to the ball in a purposeful manner. This is known as The Kinetic Chain Theory of throwing.

Six Phases of the Baseball Pitch

In order to understand the biomechanics of throwing, one must be aware of the six phases of pitching and the effect of the kinetic chain. The throwing motion of the overhead pitch has been divided into six segments or phases from wind-up to follow-through [6, 7].

Phase I

This initial stage is called the wind-up phase. During this phase the pitcher balances on the trailing push-off leg, while the stride leg reaches its maximum hip flexion. The arm is in slight abduction and internal rotation. The elbow is flexed and the forearm pronated.

Phase II

This stage is known as the early cocking phase, during which the ball is removed from the glove, the hands separate and the shoulder abducts and externally rotates. As this occurs, the ground reactive forces manifest in the lower body segments and these forces are then directed through the hip and pelvis of the push-off leg creating the forward movement of the body to generate the kinetic energy in the direction of the throw. As this push-off force increases so does the velocity of the throw. During this phase, there is increased activation in virtually all muscle groups of the shoulder girdle except the upper and lower trapezius with the highest degree of activation being observed in the upper trapezius (64% MVIC, multispectral visible imaging camera) and supraspinatus (51% MVIC) (Fig. 3.1; [8]). The elbow remains flexed between 80° and 90°.

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Fig. 3.1

Electromyographic analysis of the upper extremity musculature during overhead throwing. EMG electromyography, MVIC multispectral visible imaging camera

Phase III

The late cocking phase is characterized by maximal shoulder abduction and external rotation. The elbow is flexed 90–120° and forearm pronation is increased to 90°. During this phase, the greatest activation is noted in the subscapularis (124% MVIC) and serratus anterior (104% MVIC) [9].

Phase IV

Acceleration is marked by the generation of a forward-directed force resulting in internal rotation and adduction of the humerus coupled with rapid elbow extension. The greatest activity is again noted in the subscapularis (152% MVIC) and serratus anterior (147% MVIC). There is also a large increase in the recruitment of the latissimus dorsi (from 32% to 110% MVIC). Stage 4 terminates with ball release and lasts 40–50 msec. During this brief amount of time, the elbow accelerates as much as 5000°/s² [10]. The medial elbow structures experience a tremendous valgus stress during the late cocking and early acceleration phases. Valgus forces as high as 64 N m are observed at the elbow during late cocking/early acceleration [11].

Phase V

Deceleration begins at ball release and with all muscle groups about the shoulder maximally contracting to decelerate arm rotation. Shoulder abduction is maintained at approximately 100° while the elbow reaches terminal extension at 20° short of full extension. Eccentric biceps and triceps contraction assists in slowing down elbow extension. Forceful deceleration of the upper extremity occurs at a rate of nearly 500,000°/s² over the short time of 50 ms [12].

Phase VI

The final stage is follow-through. This phase involves dissipation of all excess kinetic energy as the elbow reaches full extension and the throwing motion is complete.

The Kinetic Chain Theory

The kinetic chain is defined as a rapid, coordinated progression of muscle activation and force development from the legs (distal segments) to the arm during the initiation of unilateral arm throwing. Muscle activation is first seen in segments from the contralateral foot stabilizing structures and progressing through the lower legs to the pelvis and trunk and ultimately to the rapidly accelerating upper extremity. This progression captures the kinetic energy and transfers it effectively up the chain to the smaller upper extremity segments, as the shoulder is not able to generate very much force by itself. The main function of the shoulder is to harness the forces from below and to direct these forces to the arm. The forces of the kinetic chain within the upper extremity then propagate from proximal to distal resulting in a high-velocity ball release.

When looking specifically at the elbow and its interplay with the kinetic chain, two main interactions are found. First, the forearm muscle groups have been noted to assist in fine-tuning ball release. Hirashima et al. [13] analyzed pitching motions and found proximal-to-distal muscle activation, peak torque development, and force development from the trunk to the elbow. In this study of the trunk and arm muscles, the muscle activation sequencing and peak intensity proceeded from the contralateral internal and external obliques and rectus abdominis muscles to the scapular stabilizers, deltoid, and rotator cuff. Force development also proceeded in this pattern. The study showed that muscle activation around the elbow did not appear to continue in this force